Firing mechanism of automatic gun



arch 26, 3945. H. TREVASKKS 2,397,387

FIRING MECHANISM OF AUTOMATIC GUNS Filed July 14, 1944 i f 5 L Q fizzr-enzor Patented Mar. 26, 1946 FIRING MECHANISM OF AUTOMATIC GUN Henry Trevaskis, Foleshill, Coventry, England, as-

signor to Dunlop Rubber Company Limited, London, England, a British company Application July 14, 1944, Serial No. 544,876

' In Great Britain September 21, 1943 7 Claims.

My invention concerns improvements in or relating to the firing mechanism of automatic guns of the kind having a reciprocating breech block, a sear serving to retain the breech block in a rearward position against spring load, said sear being displaceable against a sear spring to permit the breech block to advance to its firing position, whence the breech recoils to its rearward initial position.

It is import-ant when the gun is not firing that the face of the sear should engage fully with a shoulder or like face formed on the breech block since partial engagement between these faces may result in the inadvertent discharge of one or more rounds consequent upon vibration such for example as may be sustained by an aircraft on landing and which may suffice to free the breech block from the face of the sear when not in stable contact therewith.

The present invention has for its object to ensure full and positive contact between the scar and the breech block in an automatic manner adapted to preclude engagement of the sear with the breech block during forward movement of the latter during which movement insecure engagement or jamming may occur and to ensure that the sear may rise into position to engage the breech block only during the recoil stroke of the breech blockwhereby the sear is afforded time, before the breech block begins its next forward movement, to rise fully to its non-firing position.

According to this invention firing mechanism for an automatic gun having a breech block retained by displaceable sear against spring load comprises a spring controlled member adapted to hold the sear in a displaced position, said member being moved from its operative position by a sear contacting shoulder in the breech block when the said breech block approaches the firing position.

In order that the invention may be more clearly understood and readily carried into practical effect reference is made, in further describing the same, to the accompanying drawing in which:

Fig. 1 is a diagrammatic view of an automatic gun provided with one form of firing mechanism constructed in accordance with the invention.

Fig. 2 is a similar view showing an alternative form of firing mechanism constructed in accordance with the invention.

As shown diagrammatically in the drawing, an automatic gun of the type specified comprises an elongated hollow chamber I hereinafter referred to as the breech casing containing at its rearward end a spring loaded breech block 2 having a shoulder 3 formed 'in its base which shoulder is engaged by a sear 4 pivoted to the base of the breech casing. The sear is of generall elongated and triangular form having a substantially fiat vertical face 5 on its rearward end which face may be curved slightly and rounded at its apex to facilitate disengagement from the shoulder in the breech block. The base of the sear is extended rearwardly by a projection 6 having an aperture through which slides the stem of a sear pin 1 having a head 8 adapted to be pulled downwardly against a spring 9 by connection to a solenoid or like device energised or operated by pressure applied to a firing button or other remote firing control. The sear 4 is spring loaded in known manner to project upwardly through a slot [8 in the base of the breech casing into the path of the shoulder formed on the breech block.

The stem of the sear pin 1 is formed with a notch I 0 which on downward movement of the sear pin registers with and is engaged by the rearwardly extending and pointed end H of a detent member [2 which is reciprocably aligned beneath and parallel to the longitudinal axis of the breech casing. As shown in Fig. 1 the forwardly extending end of the detent member is provided with a toe part I3 projecting upwardly through a slot I! in the breech casing into the path of the shoulder 3 by which said toe part is struck as the breech block advances to the firing position. The rear end of the slot H in the breech casing is spaced from the forward end of the breech block a distance which may be substantiall equal to the length of that portion of the breech block between its forward end 2a and the shoulder 3 in its base. The member i2 is urged rearwardly under the control of a spring M as b a coil spring located in the slot ll between the forward end of the slot and the face of the toe part 13 projecting upwardly therethrough.

In the modification shown in Fig. 2 the forward end of the reciprocable detent member I2 is pivoted to one arm I 5 of a bell-crank pivoted at its elbow within the slot IT in the breech casing the other arm of the bell-crank being formed to present a convex cam l6 having oppositel inclined surfaces projecting through the slot into the path of the breech block whereby the bellcrank is caused to rock by sliding contact with the breech block against the load of a torsion spring I4 as the breech block moves towards or awa from its firing position.

The operation of the mechanism is as follows: On depressing the sear pin as by a connection to a remotely operable firing button such pin is drawn downwardly :thus deflecting the sear block i from its initial position against spring load and out of contact with the shoulder 3 formed in the breech block 2 whereby the breech block is permitted to reciprocate to fire the gun in known manner as long as the firing button is depressed. On downward movement of the sear pin 1 or 'I' the pointed rearward end I l of the member 12 or IE engages the notch H) in the sear pin and as long as the sear pin is depressed the end I I is reciprocated, being moved out of engagement with said notch as the breech block approaches its firing position and into engagement with the notch under spring load as the breech block recoils.

On releasing the pressure applied to the firing button the breech block on next approaching its firing position carries the member 12 or 12' forward against the spring load M or I4 to free the sear pin I or 1' which permits the sear A to ris to the initia1 position shown in the drawing during the period in which the breech block 2 reaches the forward end of it stroke and is clear of the sear. The breech block on recoil overrides the inclined surface of the upraised sear which is momentarily depressed but rises again to its initial position under spring load as soon as the breech block has tripped clear. As soon as the recoiling breech block 2 has tripped clear of the sear i the sear is raised by its spring to engage the shoulder 3 in the breech block at the beginning of its next forward movement with the certainty of full surface contact between the vertical face of the sear and the face of the shoulder formed on the breech block.

Having described my invention, what I claim is:

1. Firing mechanism for an automatic gun which comprises a reciprocating breech block retained against spring load, a sear arranged to engage said breech block, a sear-release rod connected to said sear to retain said sear from operative contact with said breech block, a reciprocable detent member positioned toengage said sear-release rod under spring load when said rod is moved to release the sear, said detent member extending forwardly and having at its forwardly extending end a part projecting into the path of the breech block in the forward position of the breech block, whereby said detent member is carried out of engagement with said sear-release rod and the sear is released when the breech block moves to firing position.

2. Firing mechanism for an automatic gun which comprises a reciprocating breech block retained against spring load, a sear arranged to engage said breech block, a sear -release rod connected to said sear to retain said sear from operative contact with said breech block, said searrelease rod having a notch, a reciprocable detent member positioned to engage the notch of said sear-release rod under spring load when said rod is moved to releas said sear, said detent member extending forwardly and having at its forwardly extending end a part projecting into the path of the breech block in the forward position of the breech block, whereby said detent member is carried out of engagement with said searrelease rod and the sear is released when the breech block moves to firing position.

3. Firing mechanism for an automatic gun which comprises a reciprocatin breech block retained against spring load, a sear arranged to engage said breech block, a sear-release rod connected to said sear to retain said sear from operative contact with said breech block, a reciprocable detent member positioned to engage said sear-release rod under spring load when said rod is moved to release the sear, said detent member extending forwardly of said sear-release rod, a bell crank lever one arm of which has a convex cam surface projecting into the path of the breech block in the forward position of the breech block, and having the other arm connected to said detent member, whereby said detent member is carried out of engagement with said sear-release rod and the sear is released when the breech block moves to firing position.

4. Firing mechanism for automatic guns which comprises a, breech block spring loaded to move toward firing" position, a displaceable sear arranged to hold said breech block in non-firing position, a notched sear pin arranged to move said sear, a spring arranged to move said pin and sear to breech engaging position, means to engage the notch of said pin when said sear has been displaced to release said breech block to hold said pin and sear temporarily in displaced position and means actuated by said breech block when said breech block is moved to firing position to withdraw said notch engaging means.

5. Firing mechanism for automatic guns which comprises a spring loaded breech block, a sear movable to engage and retain said breech block in'non-firing position, a sear pin arranged to withdraw said searvfrom engagement with said breech block, said pin having a notch, a sear spring loading said scar and sear pin toward position to engage said breech block, a spring loaded reciprocating latch arranged to engage said notch when said sear and pin are withdrawn from engagement with said breech block, said latch having a projection engaged by said breech block when said breech block is moved to firing position to release said latch from said notch.

6. Firing mechanism for automatic guns which comprises a spring loaded breech block, a sear movable to engage and retain said breech block in non-firing position, a scar pin arranged to withdraw said sear from engagement with said breech block, said pin having a notch, a sear spring loading said sear and sear pin toward position to engage said breech block, a rod movable to engage said notch, and a spring pressed bell crank lever having one arm connected to said rod to move said rod into engagement with said notch and having an arm engaged by said breech block when said breech block is moved to firing position to withdraw said rod from said notch to release said sear pin.

'7. Firing mechanism for automatic guns which comprises a breech block spring loaded to move toward firing position, a displaceable sear arranged to hold said breech block in non-firing position and having a notched element arranged to move with said sear, a detent member arranged to slide into position to engage the notch of said element when said sear has been displaced to release said breech block and to hold said sear temporarily in displaced position, said detent member having means engaged by said breech block when said breech block is moved to firing position to withdraw said detent from engagement with said notch.

HENRY TREVASKIS. 

